The present invention relates to an oblong spacer for children primarily intended to be used in conjunction with a metered dose inhaler (MDI), said spacer being rotationally symmetrical around a central, longitudinal axis and being provided with an opening at each end located centrally in said axis for connection of an MDI respectively a mouth-piece or similar.
MDIS are containers with an actuating, metering valve containing a mixture of a pressurized propellant and a drug. When the valve is actuated, a dose of the drug/propellant mixture is ejected into the air and can be inhaled by a patient.
In order to alleviate the problems of a high oral deposition and the coordination difficulties associated with MDIS, different kinds of spacer devices have been developed. A spacer device includes a holding chamber adapted to be connected to the MDI at one end. The other end of the spacer is connected to or provided with a mouthpiece and/or a face mask through which a patient can inhale. When the valve is actuated, the dose of the drug/propellant mixture is sprayed into the spacer, resulting in a cloud of smaller particles in the respirable range (an aerosol) being contained in the chamber for a certain time, during which time larger particles, that is particles that normally would be deposited orally, are separated from the aerosol dose and deposited in the spacer. The propellant evaporates at the same time. The cloud of particles can be inhaled effortlessly by the patient.
The prior art devices of this kind are however exclusively designed for use in older children and adults. Their volume normally varies from 0.5 to 2 litres and they generally are made of a polymer material, for instance polycarbonate. They are often adapted for use in younger children. The reproducibility and age-dependency of their dose-delivery when used for the treatment of children is important, but these have not yet been ascertained. Theoretical models have predicted an increased lung deposition in small children due to the smaller airway calibre and a greater ventilation/kg, but in vivo documentation is sparse. Most of the available documentation in vivo of dose delivery from the prior art devices discusses the clinical response in wheezy children from inhalations of xcex22-agonist. In these studies, the drug has been administered in doses considerably above the minimum effective dose. The response is therefore not critically dependent on reproducible delivery. The results from studies relating to these drugs further can not be extrapolated to the generation of a steroid aerosol, which has other micronizing and solubility characteristics.
Consequently there is a need for spacer delivery systems specially adapted to the treatment of young children. The need is particularly great in systems to be used in the administering of steroids due to the stricter demands on the reproducability and dosage accuracy for these drugs. A high utilisation of the substance also is desirable.
The volume of the spacer is critical since the aerosol is emptied from the chamber in an exponential manner. The inspiratory volume required to inhale the total dose of aerosol will be several times the spacer volume. The settling of particles limits the time available for inhalation. Since the inspirational capability of small children is smaller than the inspirational capability of adults, a reduction of the spacer volume might be indicated, for instance in the range of a few tidal breaths of an infant to reduce the time required for administration.
A reduced spacer volume will however contain an increased concentration of aerosols, and, accordingly, will require less time to empty. The fraction of airborne particles is however reduced due to impaction, adsorption, sedimentation and coagulation of the aerosol. This tendency will be aggravated if the spacer is made of a polymer material like polycarbonate, which may be charged by electrostatic forces, since the distance for each particle to the nearest wall will be smaller than in a prior art spacer, and the electrostatic forces will consequently have a greater influence.
The object of the invention consequently is to provide a spacer well adapted to the treatment of small children based on the above considerations.
The above object is achieved in that a spacer as described introductorily is designed to have a small total volume which is in the range between 50 and 400 ml, and in that the material in the spacer has a surface resitivity which is lower than 109 Ohm, preferably lower than 106 Ohm. In a most preferred embodiment the surface resistivity is lower than 1. Other preferred embodiments are set forth in the dependent claims.